Answer: First, transplant shock can set a plant back. Also, many sunflowers are annuals. Annuals are plants whose life cycle (vegetative growth, bloom, seed set) is completed in a single growing season. The plant dies at the end of the cycle and a new generation begins with seed germination. If you have an annual sunflower, it may just be coming to the end of its life. If you have a perennial, the biggest problem with growing sunflowers indoors is that they need lots of sun! About 8 -10 hours per day, minimum. They also like moisture, so I'd keep the soil consistently moist, but not wet. I hope this info helps.
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